Comprehensive study of the physical properties of Ba3Pn2 (Pn=N, P, As, Sb and Bi) through first principles technique

The structural, electronic and optical properties of Ba(3)Pn(2) (Pn=N, P, As, Sb and Bi) compounds have been investigated using density functional theory based on Full potential linearized augmented plane wave (FPLAPW) method, as implemented in WIEN2K package. Wu-Cohan approach is used for structural parameters; lattice constant, optimized volume, bulk modulus and its derivative. For band structure calculations Modified Beck and Johnson Approximation (mBJ) is used, which predicted these materials as small and direct band gap semiconductors. The bond lengths between Ba and Pn are also calculated. Ba-d state and Pn-p state contribute in VB as well as in CB. The bonding nature calculation indicates the strong covalent bond between Barium (Ba) and Pnictogen group situated at corner of the unit cell position and ionic bond between Ba and Pnictogen group placed at unit cell centre. The optical parameters, like dielectric function (real and imaginary part), optical conductivity, absorption coefficient, index of refraction (real and imaginary) and reflectivity are also calculated, which is the IR region of electromagnetic spectra.